1. Field of the Invention
The present invention relates to a vibrator for a vibrating gyroscope, a vibrating gyroscope using the vibrator, and an electronic apparatus using the vibrating gyroscope. More particularly, the present invention relates to a vibrator for a vibrating gyroscope for use in video cameras with a camera-shake prevention function, car navigation systems, pointing devices, etc., a vibrating gyroscope using the vibrator, and an electronic apparatus using the vibrating gyroscope.
2. Description of the Related Art
FIG. 20 shows a perspective view of a conventional vibrator 100 for a vibrating gyroscope. FIG. 21 shows a front view thereof. The basic concept behind the vibrator 100, shown in FIGS. 20 and 21, is disclosed in Japanese Unexamined Patent Application Publication No. 7-332988.
In FIGS. 20 and 21, the vibrator 100 has a first piezoelectric body 101 which is polarized in the thickness direction and has a first detection electrode 104a and a second detection electrode 104b, both having the same area, formed on one main surface thereof. The vibrator 100 also includes a second piezoelectric body 102 which is polarized in the thickness direction and has a driving electrode 105a formed on one main surface thereof. The other main surface of the first piezoelectric body 101 and the other main surface of the second piezoelectric body 102 are laminated together with an intermediate electrode 103 in between.
Furthermore, supporting members 106a and 106b which also serve the function of lead wires are provided at the positions at which node points N1 and N2, which are the nodes of vibration of the vibrator 100, are projected vertically on the first detection electrode 104a and the second detection electrode 104b, and supporting members 106c and 106d which also serve the function of lead wires are provided at the positions at which node points N1 and N2 are projected vertically on the driving electrode 105a. 
Since the end portions of the supporting members 106a, 106b, 106c, and 106d are fixed and a driving signal is applied to the driving electrode 105a via the supporting members 106c and 106d, the vibrator 100 performs a bending vibration in the thickness direction in which both longitudinal ends are free, and in which the nodes of the lowest-order mode are node points N1 and N2. Then, when an angular velocity about an axis in the longitudinal direction is applied to the vibrator 100, the vibrator bends in the width direction, and a signal containing an angular velocity signal is output from the first detection electrode 104a and the second detection electrode 104b. In the following description, the vibration in the thickness direction is called xe2x80x9clongitudinal bending vibrationxe2x80x9d, and the vibration in the width direction is called xe2x80x9ctransverse bending vibrationxe2x80x9d.
Generally, when there are variations in the characteristics of the vibration of the vibrator for a vibrating gyroscope, or the vibration of the vibrator for a vibrating gyroscope is not stable, it is difficult to accurately detect the angular velocity. Also, as for the vibrator for a vibrating gyroscope, as a result of being affected by the external environment during manufacture or during use, the vibration characteristics may change.
The conventional vibrator for a vibrating gyroscope 100 does not particularly have a means for reducing variations in vibration characteristics or a means for stabilizing the vibration, presenting a problem in that vibration characteristics may change under the influence of the external environment due to processing variations, variations in vibration characteristics occur, or the vibration of the vibrator for a vibrating gyroscope becomes unstable.
Also, a vibrating gyroscope using the vibrator for a vibrating gyroscope 100 has the problem of being incapable of accurately detecting angular velocity because the vibration of the vibrator for a vibrating gyroscope 100 becomes unstable.
Accordingly, an object of the present invention is to provide a vibrator for a vibrating gyroscope in which variations in vibration characteristic do not occur and in which vibration is stabilized.
Another object of the present invention is to provide a vibrating gyroscope capable of accurately detecting angular velocity by using a vibrator for a vibrating gyroscope in which variations in vibration characteristic do not occur and in which the vibration is stable.
Another object of the present invention is to provide an electronic apparatus capable of performing precise control of angular-velocity by using a vibrating gyroscope capable of accurately detecting angular velocity.
The vibrator for a vibrating gyroscope comprises a piezoelectric vibratable body and a first detection electrode and a second detection electrode formed on the piezoelectric body, for outputting a signal containing an angular velocity. At least one groove having a predetermined depth is provided in the piezoelectric vibrating body between the first detection electrode and the second detection electrode.
The piezoelectric vibrating body may comprise: an intermediate electrode; first and second piezoelectric bodies, each having first and second main surface, the first and second piezoelectric bodies being laminated via the intermediate electrode such that the first main surfaces of the first and second piezoelectric bodies are bonded to opposite sides of the intermediate electrode, respectively; and a driving electrode provided on the second main surface of the second piezoelectric body. The first and second detection electrodes are provided on the second main surface of the first piezoelectric body. The groove is provided on the second main surface of the first piezoelectric body along a longitudinal center line of the second main surface of the first piezoelectric body.
In the vibrator for a vibrating gyroscope of the present invention, the groove is preferably symmetrical with respect to the width direction of the first piezoelectric body.
In the vibrator for a vibrating gyroscope of the present invention, the bottom portion of the groove is preferably parallel to one main surface of the first piezoelectric body.
In the vibrator for a vibrating gyroscope of the present invention, the depth of the groove is preferably more than or is equal to 10% of the thickness of the first piezoelectric body.
In the vibrator for a vibrating gyroscope of the present invention, the depth of the groove is preferably 60% to 80% of the thickness of the first piezoelectric body.
According to another aspect, the present invention provides a vibrator for a vibrating gyroscope comprising driving means for driving the vibrator for a vibrating gyroscope, and detection means for detecting the output generated from the vibrator for a vibrating gyroscope.
According to another aspect, the present invention provides an electronic apparatus using the vibrating gyroscope.
In this manner, in the vibrator for a vibrating gyroscope of the present invention, since a groove is provided between the first detection electrode and the second detection electrode, vibration becomes stable.
In the vibrator for a vibrating gyroscope of the present invention, even when sharp temperature changes are given, variations in the angular-velocity detection sensitivity are not likely to occur.
In the vibrator for a vibrating gyroscope of the present invention, since a groove is provided between the first detection electrode and the second detection electrode, the difference between the capacitance of the first detection electrode and the capacitance of the second detection electrode is small, and stability with respect to changes in temperature is improved.
In the vibrator for a vibrating gyroscope of the present invention, since a groove is provided between the first detection electrode and the second detection electrode, and the provided groove is symmetrical with respect to the width direction of the first piezoelectric body, the difference between the capacitance of the first detection electrode and the capacitance of the second detection electrode is very small, and stability with respect to changes in temperature is improved.
In the vibrator for a vibrating gyroscope of the present invention, since the depth of the groove is a predetermined depth, the difference in the resonance frequencies of the longitudinal and transverse bending vibrations is nearly a constant value, and variations in the angular-velocity detection sensitivity are not likely to occur.
In the vibrator for a vibrating gyroscope of the present invention, since a vibrator for a vibrating gyroscope, in which variations in the angular-velocity detection sensitivity are not likely to occur, is used, the sensitivity of the vibrator can be set to be high, with the result that a detection circuit can be formed using an amplification circuit having a small amplification ratio, thereby reducing cost.
Furthermore, in the vibrating gyroscope of the present invention, since vibration is stable, and a vibrator for a vibrating gyroscope, in which variations in the angular-velocity detection sensitivity are not likely to occur, is used, it is possible to detect angular velocity with accuracy.
In addition, in the electronic apparatus of the present invention, since a vibrating gyroscope having superior temperature stability and which is capable of accurately detecting angular velocity is used, it is possible to form a precise control mechanism.
The above and further objects, aspects and novel features of the invention will become more fully apparent from the following detailed description when read in conjunction with the accompanying drawings.